Cell Polarity is a ubiquitous phenomenon in biology as it plays a key role in most cellular functions. While mechanisms of polarity determination have been defined in many eukaryotic systems we have little mechanistic understanding of how cell polarity is established or perpetuated in prokaryotes. Understanding the mechanism by which bacterial cells establish polarity is important as cell polarization is required for many bacterial processes including chemotaxis, adhesion, translocation, cell cycle regulation, virulence and pathogenesis. The establishment of a polarity axis in non-spherical bacteria that spans between the new pole, created at cell division, and the old pole, created by an earlier division, is essential for the proper localization of unipolar organelles and proteins whose localized activities are required for the aforementioned processes. The recently described protein TipN is a new-pole landmark protein that functions as a spatial and temporal cue for the establishment of the new-to-old-pole polarity axis in Caulobacter crescentus. This morphologically polarized bacterium is an ideal model for the study of bacterial cell polarity. Evidence suggests that TipN recruits and/or organizes polarity determinants that propagate positional information throughout the cell. I propose to identify these cell polarity determinants using a genetic screen and a substractive co-immunoprecipitation assay. Candidate genes obtained by these two complementary approaches will be characterized by the phenotypic analysis of their deletion and by the examination of the localization of their product tagged with GFP. I will also characterize a series of GFP-tagged TipN mutants that I have already generated to determine what regions of TipN are involved in its localization and function. Elucidating the basic mechanisms involved in bacterial cell polarity determination will generate key insights into prokaryotic cell biology, which will in turn provide a basis for the design of novel antibacterial agents. Fundamental processes that make life possible rely on the proper architecture of cells. The cells in our body possess complex mechanisms that establish and maintain their internal architecture. Similarly, bacteria possess an internal organization that is required for the ability of some to cause human diseases. I am interested in understanding the blue prints of bacterial architecture as understanding how these cells achieve internal organization is vital to our ability to combat them.